The present application claims priority under 35 U.S.C. xc2xa7119 of French Patent Application No. 99 08400 filed Jun. 30, 1999, the disclosure of which is expressly incorporated by reference herein in its entirety.
1. Field of the Invention
The present invention relates to a partially reflecting optical component generating, from an incident beam, two secondary beams, one of them being transmitted, the other one being reflected, and providing the unidimensional auto-alignment of the reflected beam with the incident beam, the respectively transmitted and reflected beams being each formed with two half-beams having matching wave fronts.
2. Discussion of Background Information
A component of this type shows indeed significant advantages in many applications such as laser sources with an auto-aligned external cavity. But a device of this type has not been designed yet nor has it been manufactured.
By auto-alignment, is meant the property of an optical system for which the properties of the outgoing light flow having little sensitivity to the orientation or to the position of the system compared to the incoming flow. The auto-alignment may be performed in two dimensions, i.e., in all the planes parallel to the direction of the incoming beam, or in a single dimension, i.e., in only one of these planes.
A laser cavity using a unidimensional total auto-aligned reflector, such as illustrated in FIG. 1, is described in the European patent application EP-95 402 073, published as EPO 702 438 B1 on Jun. 23, 1999. This reflector has two reflecting planar faces 2 and 3, supported by mirrors or by the faces of a prism. An incident beam 1 is reflected by face 2 and subsequently by face 3 and as long as these faces are perpendicular, the emerging beam 4 is reflected in the parallel direction and in the reverse way compared to the incident beam 1.
Partially transmitting mirrors are also known which are, among other things, used to provide the extraction of the light flow from most laser cavities.
The present invention makes it therefore possible to combine, in one element, the function of unidimensional auto-aligned retroreflection with the function of partial transmission. Up to now, these functions were both obtained with different components located at different positions in the laser cavity.
The invention consequently aims to offer a single component which provides both a function of unidimensional auto-aligned reflector and a function of sharing the incident flow as well.
In this respect, the invention relates to a partially reflecting optical component generating, from an incident beam, two secondary beams, one of them being transmitted, the other one being reflected.
According to the invention, the partially reflecting optical component includes:
a first completely reflecting planar face,
a second partially reflecting planar face, the second face being perpendicular to the first one,
a third completely reflecting planar face,
the first and third faces being in the same plane,
this component providing the unidimensional auto-alignment of the reflected beam with the incident beam, the respectively transmitted and reflected beams being each formed with two half-beams having matching wave fronts.
Advantageously, the invention may be obtained according to the following embodiments adapted to be associated according to all the technically possible combinations and each showing their own advantages:
the first and the second faces are the faces of a single first prism and the third face is supported by a second prism bearing a fourth face being in contact with the second face of the first prism, both prisms having preferably the same refractive index;
the beam being transmitted is sent back in parallel to the incident beam by a completely reflecting fifth face, supported by the second prism;
the fifth face is parallel to the second face, the beam transmitted being sent back in the opposite direction to the incident beam;
the fifth face is parallel to the third face, the transmitted beam being sent back in the same direction as the incident beam,
the first and second prisms are secured to one another and form a unitary block the mutual face orientations of which are controlled, whichever prism they may belong to;
one of the second and fourth faces has a partially reflecting treatment.
The invention also relates to an external cavity laser source having a partially reflecting system which is auto-aligned unidimensionally, as described above, forming the auto-aligned reflecting system and allowing the extraction of a flow outgoing from the source in the same position in the source.
This external cavity laser source may advantageously have a diffraction network in the cavity, arranged with respect to the auto-aligned reflector in the Littman-Metcalf configuration. It can be adjustable in wave length and the outgoing flow is advantageously redirected towards the network in a direction parallel to the axis of the cavity. It can also be multi-wave length with the use of a semi-conducting multi-guide chip.
According to the invention, a partially reflecting optical component generates, from an incident beam, two secondary beams, one of the secondary beams being reflected, the other secondary beam being transmitted The optical component comprises a first completely reflecting planar face, a second partially reflecting planar face, perpendicular to the first face, and a third completely reflecting planar face. The first and third faces are disposed in the same plane. The component provides unidimensional auto-alignment of the one of the secondary beams with the incident beam. The one and the other of the secondary beams are each formed with two half-beams having matching wave fonts.
According to a further aspect of the invention, the first and the second faces are faces of a same first prism and the third face is supported by a second prism bearing a fourth face in contact with the second face of the first prism. The other secondary beam is sent back parallel to the incident beam by a fifth completely reflecting face, supported by the second prism. The fifth face is parallel to the second face, the other secondary beam being sent back in the opposite direction to the incident beam. Further, the fifth face may be parallel to the third face, the other secondary beam being sent back in the same direction as the incident beam. The first and second prisms may be secured to one another to form a unitary block, the mutual face orientations of which are controlled, regardless of the prism to which they belong. One of the second and fourth faces may bear a partially reflecting treatment.
Moreover, the invention contemplates an external cavity laser source including an optical component forming a unidimensional auto-aligned reflecting system and allowing extraction of an outgoing flow from the source, the optical component generating, from an incident beam two secondary beams one of the secondary beams being reflected the other secondary beam being transmitted. The optical component comprises a first completely reflecting planar face, a second partially reflecting planar face, perpendicular to the first face, and a third completely reflecting planar face. The first and third faces are disposed in the same plane. The component provides unidimensional auto-alignment of the one of the secondary beams with the incident beam, the one and the other of the secondary beams being each formed with two half-beams having matching wave fronts.
The laser source further comprises within the cavity a diffraction network arranged in the Littman-Metcalf configuration, with respect to the auto-aligned reflector. The laser source is matchable in wave length. The cavity is folded with an additional reflecting dihedral and in that the auto-aligned reflector closes the cavity after a second diffraction on the network. The source may be mufti-wave length component directs the other secondary beam to a network in a direction parallel to an axis of the cavity between the network and the reflector to generate a beam parallel to an intra-cavity beam.
The first and the second faces may be faces of a same first prism and the third face is supported by a second prism bearing a fourth face in contact with the second face of the first prism. The other secondary beam may be sent back parallel to the incident beam by a fifth completely reflecting face supported by the second prism. The fifth face may be parallel to the second face, the other secondary beam being sent back in the opposite direction to the incident beam. Further, the fifth face may be parallel to the third face the other secondary beam being sent back in the same direction as the incident beam. The first and second prisms are secured to one another and form a unitary block, the mutual face orientations of which are controlled, regardless of the prism to which they belong. One of the second and fourth faces may bear a partially reflecting treatment.